Merge tag 'bsd-user-mmap-pull-request' of https://gitlab.com/bsdimp/qemu into staging

bsd-user mmap and exec branches from gsoc

This pull request represents the mmap and exec changes from Karim Taha
for his GSoC project.

They represent all the mmap and exec related system calls and get bsd-user to
the point that a dynamic hello-world works (at least for armv7).

There are a couple of patch check errors, but they are the lessor evil: I made
purposely bad style choices to ensure all the commits compiled (and i undid the
style choices in subsequent commits).

I pushed an earlier version to gitlab, and all but the riscv64 pipelines were
green.  Since bsd-user doesn't change anything related to ricsv64 (there's no
support in qemu-project repo, though we do have it in the bsd-user fork: coming
soon).

I think this is good to go.

https://gitlab.com/bsdimp/qemu.git

Warner

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* tag 'bsd-user-mmap-pull-request' of https://gitlab.com/bsdimp/qemu: (51 commits)
  bsd-user: Add stubs for vadvise(), sbrk() and sstk()
  bsd-user: Implement shmat(2) and shmdt(2)
  bsd-user: Implement shmctl(2)
  bsd-user: Implement shm_unlink(2) and shmget(2)
  bsd-user: Implement shm_open(2)
  bsd-user: Implement do_obreak function
  bsd-user: Implement mincore(2)
  bsd-user: Implment madvise(2) to match the linux-user implementation.
  bsd-user: Implement mlock(2), munlock(2), mlockall(2), munlockall(2), minherit(2)
  bsd-user: Implement msync(2)
  bsd-user: Implement mprotect(2)
  bsd-user: Implement mmap(2) and munmap(2)
  bsd-user: Introduce bsd-mem.h to the source tree
  bsd-user: Implement shmid_ds conversion between host and target.
  bsd-user: Implement ipc_perm conversion between host and target.
  bsd-user: Implement target_set_brk function in bsd-mem.c instead of os-syscall.c
  bsd-user: Add bsd-mem.c to meson.build
  bsd-user: Implement shm_rename(2) system call
  bsd-user: Implement shm_open2(2) system call
  bsd-user: Introduce freebsd/os-misc.h to the source tree
  ...

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>